Long-term lung function follow-up of preterm infants less than 32 weeks of gestational age

Preterm infants, particularly those with bronchopulmonary dysplasia (BPD), are at risk of lung development problems. Over the last decades, lung protective strategies have been used, decreasing the risk of chronic lung disease.

To evaluate the pulmonary function test (PFT) of preterm infants born after the introduction of lung protective strategies and to assess perinatal determinants of impaired lung function in this population.

A prospective, observational, single-center study was conducted in the neonatal unit of a high-complexity hospital. The study included newborns with less than 32 weeks gestational age born between 2012 and 2014, who were followed up until they reach school age. For the main outcome, two groups were stablished: no BPD or grade 1 BPD (no BPD/1) and grade 2 or 3 BPD (BPD 2/3).

Out of 327 patients, 116 were included. BPD was diagnosed in 49.1% (47), with 50.9% (29) classified as grade 1, 35.1% (20) as grade 2, and 14.0% (8) as grade 3. Mean age at PFT was 8.59 years (SD 0.90). Mean FEV1% was 95.36% (SD 13.21) and FEV1 z-score -0.36 (SD 1.12); FVC% 97.53% (SD 12.59) and FVC z-score -0.20 (SD 1.06); FEV1/FVC ratio 85.84% (SD 8.34) and z-score -0.24 (SD 1.34). When comparing patients with no BPD/1 and BPD 2/3, we observed differences in all pulmonary function parameters, which persisted after adjusting for gestational age. No differences in PFT were observed between patients without BPD and those with grade 1 BPD. Most patients (76.7%, 89) had normal spirometry pattern, with obstructive pattern observed in 12.9% (15), restrictive pattern in 9.5% (11), and mixed pattern in 0.9% (1) of patients.

Preterm infants with BPD 2/3 showed a decrease in all pulmonary function parameters compared to preterm infants with no BPD/1; an effect that was independent of gestational age. Among patients with BPD who had an altered PFT pattern, the most common pattern was obstructive, followed by restrictive and then, mixed.